Climbing Fern Fossil | Lygodium kaulfussii | Green River Formation | Wyoming

Lygodium kaulfussii
Eocene (51.98 Million Years Ago)
In Stone Fossils Private Quarry
Green River Formation, Wyoming, USA

Plate approx. size: 3" x 3" x 0.75"

Specimen approx. size: 0.5" x 0.5"

This specimen represents the fertile branch of the plant, featuring the spore-bearing fertile leaves of the species. Examples like this are relatively uncommon.

Lygodium kaulfussii belonged to a group of climbing ferns that still exist today in tropical and subtropical regions. Unlike most ferns, Lygodium species grow as vines, with fronds that twist and climb over nearby plants as they grow.

In this fossil, you can see the delicate structure of the branch - slender stems with finely detailed leaflets (pinnae) arranged along the central rachis. The fine preservation of the veins and leaf shapes tells us the frond settled gently into soft lakebed sediment, where it was buried in oxygen-poor mud that prevented decay.